December 2007
doc.: IEEE 802.22-07/0566r0
IEEE P802.22
Wireless RANs
Further Inquiry into Letter Ballot #2 Comments 34, 35, 45, 105,
466, 473, and 477 pertaining to Annex C Assumptions in Draft
P802.22.1/D2
Date: 2007-12-11
Author(s):
Name
Stephen
Kuffner
Company
Motorola Inc
Address
Schaumburg, IL
Phone
email
847-538-4158
Stephen.Kuffner@
Motorola.com
Abstract
This contribution contains summaries of technical comments made in Letter Ballot #2 of IEEE
802.22.1 (Oct. ’07) that pertain to assumptions for the antenna gain and propagation model described
in Annex C of P802.22.1/D2 [1], and seeks further information in an effort to resolve these comments
to the commentor’s satisfaction.
Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the
contributing individual(s) or organization(s). The material in this document is subject to change in form and content after
further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution,
and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE
Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit
others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and
accepts that this contribution may be made public by IEEE 802.22.
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures
<http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known
use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with
respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the
Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in
the development process and increase the likelihood that the draft publication will be approved for publication. Please notify
the Chair <Carl R. Stevenson> as early as possible, in written or electronic form, if patented technology (or technology under
patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you
have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>.
Submission
page 1
Stephen Kuffner, Motorola
December 2007
doc.: IEEE 802.22-07/0566r0
Introduction
Annex C in [1] was inserted into draft 2, based on work first presented in [2], as an informative technical
justification for the sensitivity and adjacent channel rejection specifications (Clauses 6.8.6, 6.8.7 in [1]). Several
comments questioned the analysis and assumptions, in particular the channel model and the beaconing device
transmit/receive antenna gain. In the following, the comments are excerpted from [3] and initial responses
seeking further information are addressed to the commentors.
Discussion
34
The scenario used for the link analysis is an ideal situation which appears
impractical for implementation.
TR
Comment Type
Base the analysis on a worse case scenario.
Proposed Remedy
Charles Einolf (c.einolf@ieee.org)
Commenter
Response: The presented scenario used simple two-ray propagation plus 20 dB shadowing and 12.5 dB fading. It
would help if you could give a detailed description of, and justification for, the worse case model that would be
acceptable for inter-beacon communication and desired range (note that annex C is not about protection range, but
inter-beacon communication range for two beacons attempting to aggregate).
Comment #
Comment
35
The assumed receive antenna gain is an ideal case and may not be representative of
a omni-directional wideband antenna mounted on a vehicle close to ground level.
TR
Comment Type
Consider the use of a worse-case scenario for the receive antenna gain in this
Proposed Remedy
situation.
Charles Einolf (c.einolf@ieee.org)
Commenter
Response: The present antenna gain assumption is 7 dBi. Please suggest an appropriate worse case Rx antenna
gain and EIRP the broadcasters would agree to.
Comment #
Comment
45/105
The assumption of a 7 dBi antenna gain for the beacon implies a physical
implementation which might be impractical. Yet without this gain, which was also
used to calculate beacon link margins, the protection offered by the beacon would
be compromised.
TR
Comment Type
Clarify how the 7 dBi antenna gain would be obtained in practice, and if possible,
Proposed Remedy
give some example antenna implementation details. Alternatively, propose other
ways to achieve the same link performance.
Chris Clanton (Clanton_Christopher@shure.com), Edgar Reihl
Commenter
(Reihl_Edgar@shure.com)
Response: There are several parameters that impact the protection range. See e.g. [4] and [5] in the March ’07
link on the 802.22 “meeting documents” site. This analysis was framed around the determination of the beacon
data rate to satisfy the link margin (beacon should be detectable as far away as it can be interfered with). Here is a
list of the parameters in Eq. (4) of [5]:
Comment #
Comment
Submission
page 2
Stephen Kuffner, Motorola
December 2007













doc.: IEEE 802.22-07/0566r0
Pb: the beacon transmit power (not EIRP but TPO);
Pw: the WRAN transmit EIRP;
Δ: the path loss difference due to antenna height (function of hb, beacon antenna height, and hm, the
microphone rx antenna height, nominally assumed to be 1.5 m);
Gb,tx = beacon Tx antenna gain (with Pb gives beacon EIRP);
Gm,rx = microphone receiver antenna gain;
F↑ = upfade margin (WRAN into microphone receiver);
Gw,sens = WRAN sensing antenna gain;
NFw = WRAN’s TG1 receiver noise figure;
NFm = microphone Rx noise figure;
Es/No,min = minimum beacon Es/No required to satisfy desired packet error rate;
I/Nmax = maximum tolerable interference-to-noise ratio of WRAN interference to microphone Rx
noise;
Bb = beacon bandwidth (= symbol rate);
Bw = WRAN bandwidth.
These parameters are adjustable in link margin spreadsheet [4]. The equation used to determine the beacon
symbol rate given all other parameters was
P B 
10 log b w     Gb,tx  Gm, rx  F   G w, sens  NFw  NFm  E s / N o, min  I / N max  0
 Pw Bb 

P 
B 
10 log b     Gb,tx  Gm, rx  F   G w, sens  NFw  NFm  E s / N o, min  I / N max  10 log b .
 Pw 
 Bw 
The equation can also be framed with a given beacon bandwidth to solve for the minimum Es/No. This is used to
calculate link margin for a given symbol rate. That equation is
P B 
10 log  b w     Gb,tx  Gm,rx  F   Gw,sens  NFw  NFm  I / N max  E s / N o,min
 Pw Bb 
With all other parameters remaining the same, an e.g. 5 dB decrease (e.g. to 2 dBi) in Gb,tx results in a 5 dB
decrease in Es/No,min. That is, the modulation has to deliver the desired detection probability for a 5 dB lower
Es/No (e.g. 25 dB instead of 30 dB). Some other parameters can be changed to compensate, while some others
probably aren’t negotiable. If Gb,tx gets e.g. 5 dB smaller, it can be compensated by (either individually or in some
combination that adds up to 5 dB):
Reducing
o Es/No,min (consequence: worse beacon detection PER for same modulation and coding or need
more robust modulation + coding)
o Pw (consequence: shorter range WRANs – this was proposed at the March ’07 meeting for the
grouped subcarrier mode, no longer used),
o Bb (consequence: beacon message takes longer to receive  longer quiet periods for WRANs),
o Gm,rx (consequence: reduced microphone range),
o NFw (consequence: tougher WRAN TG1 receiver design), or
Submission
page 3
Stephen Kuffner, Motorola
December 2007
doc.: IEEE 802.22-07/0566r0
Increasing
o Δ (consequence: greater beacon antenna height),
o Gw,sens (consequence: more complicated sensing antenna – we had proposed using the WRAN link
antenna for this purpose at the March ’07 meeting, which could cover the difference itself, but
this adds complications since link antenna pattern and polarization is not appropriate for sensing
other types of signals (e.g. DTV)),
o I / Nmax (consequence: degraded N+I floor at microphone receiver – reduced microphone range).
These parameters will have different costs per dB of change. If those costs could be established (requires inputs
from the group), a minimum cost solution could be proposed.
466
I have concerns about the validity and practicality of the assumptions used in the
link analysis, particularly the assumption of 7 dBi antenna gain, without which the
area protected by the beacon would be much smaller.
TR
Comment Type
Consider worst-case, or less-ideal-case, assumptions.
Proposed Remedy
Tom Gurley (tgurley@ieee.org)
Commenter
Response: See above. This annex is not about the protecting area but the inter-beacon communications range.
Please come to agreement and suggest an appropriate worse case antenna gain. The inter-beacon communications
range will be smaller with lower EIRP and Rx antenna gain and no other system changes. Whether it is “much
smaller” as suggested in the comment depends on the propagation model and the antenna gain change.
Comment #
Comment
473
There are questions about the Link Margin as described in Appendix C.
Assumptions about parameters in the appendix would impact the ability of the
beacon to provide agreed protections, if they turn out to be invalid or impractical.
In particular, it is not clear what are the assumptions around the 7 dBi antenna gain
number and without that, the beacon coverage area would be smaller.
T
Comment Type
None.
Proposed Remedy
Jerry Kalke (jkalkesr@att.net)
Commenter
Response: As above. Please be more specific about the “agreed protections.”
Comment #
Comment
Comment #
Comment
Comment Type
Proposed Remedy
Commenter
Submission
477
The beacon protection bubble afforded to wireless microphone is based on a
number of assumptions and parameters in Annex C. if these
assumptions/parameters can not be realized in the field, they could severely limit
the level of protection of the beacon. One such parameter is the effective gain of
the beacon antenna (7 dBi). Such an antenna gain requirement is quite stringent on
the incumbent and may be not easily realizable in the field. Different assumptions
need to be examined.
T
Suggest to conduct the analysis with a lower gain antenna i.e 2 dBi, and determine
the impact on the level of protection. Another is to increase the output power of the
beacon.
Victor Tawil (vtawil@mstv.org)
page 4
Stephen Kuffner, Motorola
December 2007
doc.: IEEE 802.22-07/0566r0
Response: Annex C is about inter-beacon communication, not about the protection bubble around a microphone
deployment. The protection zone around a microphone deployment was discussed in March ’07 (where the 7 dBi
antenna gain was first used and has been the assumption since then) in several presentations based upon
documents [4] and [5] (see March ’07 link on 802.22 site). The protection bubble was analyzed without a
propagation model since the main interest here is bulk path loss, assumed to be roughly symmetric between the
beacon Tx and WRAN sensing Rx (the detection path) and the WRAN Tx and the microphone receiver Rx (the
interference path), except for accounted-for differences in antenna heights and narrowband fading. The reason for
avoiding the channel model vs. range here was that it really doesn’t matter; all that matters is the path loss.
Submission
page 5
Stephen Kuffner, Motorola
December 2007
doc.: IEEE 802.22-07/0566r0
References:
[1]
[2]
[3]
[4]
[5]
P802.22.1/D2, “Part 22.1: Enhanced Protection for Low-Power, Licensed Devices Operating in
Television Broadcast Bands,” October 2007.
IEEE 802.22-07/0440r1, “Sensitivity and Adjacent Channel Rejection Considerations, Addressing
Comments 39, 70, 171, 208, 214, 354, and 408,” Steve Kuffner, August 2007.
P802 22 1d2 0_cmts_005.xls, “802.22.1 Letter Ballot #2 Comments Resolution Database,” Monique
IEEE 802.22-07/0148r0, “802.22 TG1 Link Margin Calculator,” Steve Kuffner, March 2007.
Brown, Dec 2007.
IEEE 802.22-06/0195r3, “Interference-Based Bandwidth Constraints for Proposed IEEE 802.22 TG1
Transmitters,” Steve Kuffner, March 2007.
Submission
page 6
Stephen Kuffner, Motorola